AJP - Gastrointestinal and Liver Physiology, Vol 245, Issue 4 597-G600, Copyright © 1983 by American Physiological Society
Pentagastrin potentiates nonadrenergic inhibitory neuromuscular transmission in orad stomach of the dog
P. F. Schmalz, K. G. Morgan and J. H. Szurszewski
Mechanical and intracellular electrical activities were recorded separately
from circular muscle of the orad corpus of the canine stomach. In normal
Krebs solution, transmural electrical nerve stimulation produced excitatory
and inhibitory responses. The excitatory response was blocked by atropine;
the inhibitory response was unaffected by phentolamine or propranolol alone
or in combination. Both responses were blocked by tetrodotoxin. In the
presence of pentagastrin, the inhibitory response to electrical nerve
stimulation was potentiated in a dose-dependent manner. The threshold
concentration for this potentiating effect was 3 X 10(-11) M. Intracellular
recordings showed that hyperpolarization of the resting membrane potential
in response to inhibitory nerve stimulation was greater in the presence of
pentagastrin than in its absence. These data suggest that, in addition to a
direct stimulatory effect on the muscle, pentagastrin also potentiates the
effect of ongoing activity of intramural inhibitory nerves. This latter
effect is only apparent when the inhibitory neural network is active. Thus,
the in vivo effect of pentagastrin on motor activity of the corpus will
depend on the degree of ongoing activity of intramural inhibitory nerves.
